In the six weeks since Denise Richards filed for divorce from husband Charlie Sheen, the two have been walking a fine line between civility and standoff. They've spent time together at their daughter Sam's first birthday party March 12 and, more recently, celebrated Easter Sunday at the Agoura Hills, Calif., home they shared until Sheen moved out earlier this year. But with a custody battle looming and allegations that Sheen has fallen back into his old vices (he denies it), that line may soon be crossed.

In her recent divorce filing, Richards, 34, took the unusual step of requesting sole legal custody of Sam and the couple's unborn child (Sheen requested joint custody). The move, if successful, would mean that Sheen, 39, can no longer make decisions about the health and welfare of his children—though he could have visitation. "She'd have to prove it's in the best interest of the children," says lawyer Lynn Soodik, "and that either he refuses to communicate with her regarding decisions about the children or that his judgment is impaired." A rep for Richards has no comment, but Soodik says she may have an advantage in the short run. If Richards breast-feeds when she delivers in June, it will be difficult for Sheen to spend extended periods of time with the baby—or with Sam, since a judge maybe reluctant to separate the siblings. But despite the legalities, a friend of Richards's says that "Denise expects Charlie to be a part of their children's lives. She's not looking to cut ties with him as a father."