Zoe McLellan gave her ex-husband, J.P. Gillain, only 2 days' notice before she flew to Canada with their young son for a role alongside Kiefer Sutherland ... but she says she had no choice.
McLellan is embroiled in a custody war again with Gillain. They have joint custody of 4-year-old Sebastian. McLellan says she was recently offered a gig on "Designated Survivor" and had to be in Toronto STAT to film ... but wouldn't go without Seb.
In court docs, obtained by TMZ, McLellan says she's the primary parent, adding Gillain can't support the lifestyle she offers their son. That's why she claims he needs to be with mom while she films for a year ... but she says she'll help out with dad's travel costs so he can come visit.
For his part, Gillain says his ex-wife basically held a gun to his head, demanding he consent to the move and agree to work out a new custody deal. He also argues she can't uproot their kid just because she gets a new role, arguing Seb needs stability and continuity.
He's asking a judge to order the boy back immediately.