What a good question. How would you declare it? Unless you're carrying a cold wallet, right? But then, that means the government would have to know what one of those looks like in luggage...
The government will always want to regulate and monitor because they want their cut. But to make it widespread, they government does need to endorse it.
I think it'll take a major player to come in and set the trend. Right now it seems as if a good amount of countries are too unfamiliar, so they default to just not allowing it. But then you have places like Switzerland who have issued blockchain passports. Maybe if the US or China chooses to somehow implement and regulate, ICO's will be allowed again. With cryptocurrencies, it can be hard to regulate if people don't cash out. Great insight on this thread.
The government is still trying to find ways to regulate ICO's. The IRS is scrambling to find a quick solution, but of course at the government's pace, I give it a couple of years. That's why our government needs to partner or hire good talent to develop this aspect that they're lacking.