Kurt Busch will be able to return to NASCAR Sprint Cup Series competition this weekend at Phoenix International Raceway, after NASCAR reinstated the former champion less than three weeks after putting him on indefinite suspension.

Busch was placed on suspension on February 20 in the wake of a damning report from a family court commissioner in the state of Delaware that concluded the 36-year-old had "more likely than not" assaulted former partner Patricia Driscoll in his trailer at Dover International Speedway last September.

Driscoll filed a domestic abuse complaint against Busch last November, and won a protection order that requires Busch stay 100 yards away from her at all time and make no attempt to contact her for the next 12 months. Busch has also been told he cannot own or buy firearms or ammunition during that period, and that he must undergo a psychiatric evaluation for "mental health problems related to anger control and impulse control."

Since the family court's decision, the Delaware Attorney General's office has announced that it will not be filing criminal charges of domestic abuse against Busch following a two-month investigation by Dover police into the incident after concluding that "the admissible evidence and available witnesses would likely be insufficient to meet the burden of establishing beyond a reasonable doubt that Mr Busch committed a crime."

Since the Attorney General's decision not to press criminal charges was made public last week, there has been pressure on NASCAR to reconsider its decision to suspend Busch which has led to today's surprise announcement.

"NASCAR announced today that, effectively immediately, the indefinite suspension of Kurt Busch has been lifted," said a statement from the sanctioning body released on Wednesday morning.

"He is eligible to return to NASCAR racing under indefinite probation subject to additional mandatory requirements that include but are not limited to participation in a treatment program and full compliance with any judicial requirements placed upon him."

NASCAR noted that Busch had complied with all requirements in its reinstatement program that had been agreed 11 days ago, and that he had completed the mandatory behavioural assessment sessions.

The behavioural health care expert appointed by NASCAR to conduct the sessions had recommended to the sanctioning body that the driver be allowed to return to competition. Busch must still undergo additional steps to address the behaviour for which he was penalised.

NASCAR also confirmed that Busch would remain Chase-eligible despite having missed events at Atlanta and Las Vegas while undergoing suspension. Under the normal rules for the Sprint Cup Series, only drivers who take part in qualifying and/or race at each of the 26 regular season events can make it into the post-season Chase play-offs that decide the title.

"The requirement that a driver must compete in all championship events of the current season to be eligible for the Chase for the NASCAR Sprint Cup has been waived for the period of Kurt Busch's suspension," the statement said.

Busch would have to win one of the remaining 2015 regular season events or else qualify on championship points. He would also need to finish in the top 30 in the standings to be considered for a Chase place. Currently, Busch has no championship points at all since he has been suspended for all three races of the season, his suspension having been handed down two day before the season opener at Daytona.

"As we stated last week, the elimination of the possibility of criminal charges removed a significant impediment to Kurt Busch's return to full status as a NASCAR member," explained Steve O'Donnell, NASCAR's executive vice-president and chief racing development officer.

"We therefore have decided to move him to indefinite probation and waive the Chase requirement," O'Donnell continued. "He has fully complied with our reinstatement program during his suspension and the health care expert who conducted his evaluation recommended his immediate return.

"We have made it very clear to Kurt Busch our expectations for him moving forward, which includes participation in a treatment program and full compliance with all judicial requirements as a result of his off-track behaviour."

Busch's race team Stewart-Haas Racing issued a brief press release on Wednesday welcoming NASCAR's decision.

"We appreciate the steps Kurt Busch has made while following NASCAR's process for reinstatement," read the statement. "He has taken this path seriously, which allowed him to return to our race team. With his reinstatement and the conclusion by the Delaware Attorney General to not file charges, our focus is on the future."

Regan Smith has been deputising for Busch in the #41 SHR Chevrolet since the Daytona 500 in February.

By coincidence, Kurt's brother Kyle is also out of competition at the moment following a serious crash at Daytona that resulted in a broken right leg and a mid-foot fracture to his left foot. Kyle will continue to miss races for the foreseeable future, but is making progress with his recuperation.

Kyle's wife Samantha posted pictures on Twitter on Tuesday showing Kyle being fitted with walking boots in place of the soft casts he had been wearing since surgery over two weeks ago.

Penalties for Cup teams after Vegas

Two NASCAR Sprint Cup teams incurred post-race penalties at Las Vegas Motor Speedway last weekend, details of which were announced on Tuesday.

Brad Keselowski's #2 Penske crew has been penalised for a rules infraction committed when it was discovered that the right and left rear quarter panel wheel openings were modified after qualifying inspection on March 6.

Deemed a level 2 penalty in NASCAR's new six-tier system of working out the severity of infractions, it means that crew chief Paul Wolfe has been placed on NASCAR probation through to the end of the year. There are no points deductions or fines, or any penalty against Keselowski himself.

Also penalised was the HScott Motorsports #51 team after NASCAR found that Justin Allgaier's car did not meet the minimum weight requirement during post-race inspection. Weight ballast had been observed falling off the #51 car during Sunday's race in breach of the rule stipulating that any such added ballast must be secured in a manner that will prevent movement during an event.

NASCAR decided that this was a slightly more serious matter worthy of a P3 penalty, which means that crew chief Steve Addington has been fined $25,000.

Get the latest NASCAR news straight to your Twitter feed! CLICK HERE to follow Crash.net's new dedicated NASCAR Twitter feed