Question: I recently got my US visa and I am really happy about it. Also, I recently saw a documentary where a US immigration officer was denying entry to some people. I never thought your entry could be denied if your visa was valid.

What are common reasons for US immigration officers to deny entry in the country?

Answer: 
Any visa is never an automatic permission to enter the USA, and that’s clearly stated in many places during the application.

The core reasons to get rejected are that the officer has the impression that you are either

* going to violate the limits of the visa,
* lied in the application, or
* have a criminal intent.

The details depend on the visa—with a tourist visa, if it seems you are planning to work it is a problem—and it does seem that you are planning to work if you don’t seem to have enough money.

Most visas also have a limit for the duration of your visit, and if you don't have a return ticket, or only a vague idea where you will go, it looks fishy, etc.
A visa is not a right to enter a country. Citizenship is that.

When you enter a country, two things happen.

* An **immigration** officer speaks to you as you enter.
* The **customs** service looks at your stuff.

Those people have access to all your data in the computer, so they know all about your visa application. **If the conversation or your stuff suggests an intent contrary to law or your visa conditions**, that could lead to a refusal. For instance, on a UK border-patrol TV show, someone's luggage was found to be full of business clothing and 20 copies of the person's CV. That was *prima-facie* evidence of "seeking employment", not allowed on their visa or [VWP](https://en.wikipedia.org/wiki/Visa_Waiver_Program), so back they went.

So it is possible to have a valid visa, and then "put your foot in your mouth" at the entry interview, or be seen bringing in something foolish. For instance, it's a lousy time to try to smuggle cigarettes - people still do that, and still get turned away. (Trust me: they have cigarettes in stores here.) What makes it smuggling is "not declaring it" - declaring it greatly improves consequences for honest ordinary mistakes.

Because America is a *federal* country, this can blind-side people since we have a cacophony of differing government laws. Many states are simpatico with marijuana use, but it's a Class 1 narcotic to the feds. So drug paraphernalia or the smell of pot will doom you, even if it's legal in the state you are landing. (This is *especially* a problem at the Canada border.)

Speaking of that, border guards can prohibit things that are legal in both places - Canada won't *let in* marijuana and paraphernalia, even though it's legal in Washington state, and legal federally in Canada. A laptop full of porn is a problem here.

Note that they can also inspect your phone and your social media activity both for contrary-to-visa activities and simply being undesirable... and if you say "well, I won't give them my passcode!" they will simply refuse you entry. So data hygiene is a good plan... also, not being a jackass on social media they know about.