The US authorities reserve the right to deny travelers entry into the US. There is no type of visa or travel authorization which guarantees entry into the country, including EVUS. However, if your EVUS application has been approved, it is very unlikely that you’ll be refused entry into the US.
There are many possible reasons why you could be denied entry into the US. According to the Department of Homeland Security website, visitors can be refused entry for the following reasons:
Being refused entry into any country is stressful and the most important thing is to remain calm. Getting angry will not reverse the decision
In this situation you need to speak to your airline to get a return ticket. They may put you on a return flight free of charge, charge a fee or require you to buy a ticket for full fare (in these cases you might be able to make an insurance claim providing you have a policy).
You also have the option of seeking legal advice. A lawyer may be able to overturn decisions in some cases. If they can’t help overturn the decision they may be able to make it possible for you to return to the US in the future.
There is no way to guarantee entry into the US. However, you can take steps to minimize the chances of being denied entry.
You should make sure all your paperwork is in order. If you need to apply or renew anything, do it with plenty of time to spare. When traveling to the US, make sure you have all the necessary documentation.
If there is anything in your past which could lead to a denied entry, such as a criminal conviction or a past denied entry, speak to a US immigration attorney before you travel. They will be able to advise you what you can do to maximize your chances of entering.