KEVIN FEDERLINE has called an emergency hearing in his custody battle with Britney Spears, amid allegations his ex-wife has failed to comply with court-ordered drug tests. Lawyers for both parties are due to meet in a Los Angeles court on Thursday (08Nov07), after Federline's attorney, Mark Vincent Kaplan, called the hearing. Spears and Federline are not expected to appear in court. Under the latest court ruling, Spears is allowed to see her boys - Sean Preston, two, and Jayden James, one - three times a week, but must follow an earlier court order to undergo mandatory drug and alcohol tests and well as attend joint parenting sessions with dancer Federline. If Spears is proved to have violated the drug-testing procedures, she faces having her visitation rights suspended until she follows the court order. But the singer isn't letting the latest allegations affect her daily errands - she was spotted taking a break from her custody battle by going car shopping at California car dealership, Van Nuys Mercedes, on Wednesday (07Nov07).