I'm wall mounting a tablet and need to supply 5V.  I've seen posts on how this can be achieved but my question is specifically about these types of power supply modules:
[![enter image description here][1]][1]


https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=AC-DC+Power+Supply+Module+AC+1A+5W+220V+to+DC+3V+5V+9V+12V+15V+24V&_sacat=0

Is it legal in the USA to add an inline power supply like this behind a light switch or outlet in an outlet box?  

**EDIT:**
So from all the great discussion here the best solution is to use a recessed electrical box plus an outlet with USB
[![enter image description here][2]][2]
[![enter image description here][3]][3]


  [1]: https://i.sstatic.net/2WwDq.jpg
  [2]: https://i.sstatic.net/HlDjx.jpg
  [3]: https://i.sstatic.net/7gCCU.jpg