Looks like things are heating up between Federline and Spears again. Kevin Federline’s defense team has delivered a subpoena to the rehab facility that Spears stayed in earlier this year. The subpoena was served early Saturday morning.

Kevins team is on a subpoena spree. They’ve served subpoenas to Spears bodyguard Daimon Shippen, former assistant Shannon Funk, and her friend Alli Sims. Who’s next?

“Kevin and his attorneys Mark Vincent Kaplan and James Simon are on a mission,” says the source. “They are pursuing all relevant evidence from every potential source and every available witness.”

It appears that Federline’s team wants to know how Spears responded to therapy at Promises. For instance they probably want to know if she was resistant to treatment or if she had a good attitude during her stay.

It’s presumed that the team is gathering information for an upcoming custody battle royale.