Birkhead's publicist released a statement on Monday saying he's retained the services of celebrity attorney Debra Opri, whose past clients include James Brown.
The rep also said that Smith has been served with papers in the Bahamas, where last week she held a commitment ceremony with her attorney, Howard K. Stern, who also claims to be the baby's father.
Asked why Birkhead decided to file suit, Opri told PEOPLE Tuesday that he wants Smith and her child to return to California for DNA testing. "He wants to establish legally that which he already knows personally – that he is the father and he has rights," Opri said.
For now Smith's Bahamian attorney, Michael Scott, is not concerned with the filing. "It doesn't have any effect, because obviously jurisdiction of any court is territorial," Scott tells PEOPLE. "They can't compel her to go back."
However, Scott conceded that if Smith goes back to California, where she would be subject to the law, "she could be in difficulty."
Opri said she hopes the U.S. courts will compel Smith to return to the state. "This is an urgent issue that needs to be resolved and we are seeking the court's order to have her return to this jurisdiction for testing," she told PEOPLE.
Opri also told USA Today that Birkhead is seeking "a presence in this child's life." She added: "He is concerned for the health and safety of the child based upon drug issues and manipulation by a third party for purposes contrary to the interests of the child."
Stern revealed on Larry King Live Sept. 26 that he had loved Anna Nicole "for quite some time," and said that "based on the timing of it, there shouldn't be a doubt" that he is the baby's father.