Lets Get Real:
The sanctions go after people and companies that trade with North Korea, the point being these individuals can either trade with the North Korea and lose links with the US or cut links with NK and carry on their business interest with the US. The UN has placed tough sanctions already on North Korea, and they have not worked, China will only go so far, it does not want the NK to fall, then it would have millions of refugees coming over the border in to China. This gradual path is following the path of every other US Administration, it is pushing the can down the road, it seems that Trump is afraid of taking action, that has been the Oval Office view since President Clinton in 1994. At some point the US either has to accept a nuclear armed North Korea and place nuclear weapons in South Korea and Japan or take action, it one of the two, either war or modern appeasement.