We must stay in the European Union
We need to stay IN in union.
First, the EU membership is all that maintains the existence of what human rights laws we have (although I would strongly favour us having our own rights laws, instead of merely having a pointer to the EU laws). We should aim to duplicate the EU human rights laws into the UK law canon.
Second, the EU is our single biggest trading partner. That will remain true whether we are in or out. However, remaining in means we get a say in what those rules are. It also means we aren’t affected by the additional “EU import taxes” that would cripple our exports’ competitiveness were we outside the EU.
The idea that the USA or the Commonwealth nations would pick up the slack if we had to reduce trade with the EU is a false one. These countries already have their own integrated trade markets, and any UK trade would have to compete with them; they additionally have the competitive advantage of shorter distances, resulting in reduced transport costs and a competitive advantage compared to any UK exports Essentially, there is a reason we don’t already trade with them, and that’s because we can’t compete as it is in those markets.