Chinese licenses
When you join a Chinese company, for the government companies your license is contractually linked to that company. If you leave that company, any other company you join needs to have your license released to them. Additionally, when you leave a Chinese company, the no-incident record can be refused to be given, even though Chinese companies demand it of any other party. The mix of communism and capitalism has some lumps in it.
Beware before you sign with any chinese company. Of course there are private companies trying the same act, which is pretty interesting as a legal stance, a 3rd party withholding your right to work and intellectual property and property without a contractual right to do so. Again, look before you leap over the Great Wall...