Yes, it is an ‘interesting’ process.
The default is supposed to be maintaining the current EU law. Which will then be reviewed and amended to suit us in our new state of freedom™ as and when parliamentary time allows.
That is certainly one part of what people are concerned about.
The other part is that even where current UK law provisions are fine, being a member of the EU and having to maintain at least their standards on things and having the ECJ to decide whether provisions did meet the standards, etc. made it a lot harder for politicians to reduce protections in all sorts of areas.
Now that we leave the EU, the concern is obviously that the government is not more likely to increase protections (since despite what they would like to tell us in most cases you are perfectly free to provide for higher standards and protections than EU law requires). The inference has to be that leaving the EU provides greater opportunity to reduce protections.
One area causing a lot of concern (especially for me) is employment law. There are any number of provisions (many of which UK governments actually pushed for - as with a lot of EU law) which are very unpopular with some businesses and a lot of the current crop of politicians.
Conservative governments have frequently bemoaned the fact that EU law prevents them from accommodating the needs of business/making things easier for their cronies (delete whichever suits the reader’s political preferences
).
This is a relatively recent example under the Tory/LibDem coalition which gives a reasonable idea of the sort of aims they would like to achieve:
Animal welfare is another example. One of the things that held up TTIP was the US’s comparatively terrible food standards provisions. Not surprisingly EU farmers (and consumers) weren’t keen to have their market flooded by US standard foodstuffs.
We tend to prefer rather fewer chemicals in our food (or at least different ones). We’re not keen on GM foodstuffs being included in our food without at least telling us about it and so on.
Once we’re out of the EU, we will of course be free to do our own trade deal with the US (which we are reliably assured your president is only waiting to hand us).
The concern that perhaps our politicians won’t be too keen to jeopardise any deal by insisting on not allowing the US to say flood our markets with chlorinated chicken or pigs pumped full of antibiotics is quite high and I think realistic.