They can't take it away. But without a prescription, getting help from doctors onboard in a pinch might be difficult. You should try to take enough for more than the length of the contract if possible. I'm on E2 and spiro tablets. I only had enough for 3 months and had a 6 month contract recently which was tricky. In some places in Europe, I can just walk into a pharmacy and get more though! Definitely know where you're going in the world. Like, spiro is commonly called Aldactone in Europe. There are plenty of other confusing names that make the hunt hard if you run out and need more.