I assume the gates the OP is referring to is at the bear viewing platform....
There is absolutely no overnight parking there as the sign states parking lot is closed 930pm to 630am :
September 2013 :
As Joe mentioned, there is no US Customs stationed in Hyder as you just drive in :
Notice the paved road in place now, as in 2010 on my first visit the roads in Hyder were not paved, as a local told me the paved road project finished in October 2012....
The main road, the road to the boat launch and parking lot itself, and the roadway leading to the bear viewing platform at Fish Creek is now paved (4 to 5 miles of paved roads now) :
Hyder Boat Launch Parking Lot :
Fish Creek and Bear Viewing Station (pavement ending at far end of parking lot) :
There is a $5 fee (US or Canadian is accepted) and is good for one day as they stamp the yellow card you will receive when I showed up in the early evening.....I later on went back to the attendant and paid an extra $5 in advance for the following day so I wouldn't have to wait in line when I planned on returning, however the attendant was in a good mood and slid me back the $5 and validated my pass for the following day as well, so if you arrive during the early evening hours and plan on a following day visit....they might validate the pass for the following day without paying twice.
I did not notice any no overnight parking signs at the boat launch area itself as I suppose one could park there overnight, however that is the farthest point south from the bear viewing station (roughly 5 miles away).
I stayed at Camp Run-A-Muck which is $20 overnight (also US or Canadian accepted), nice guy that runs it...roughly 3 miles or so from the bear viewing site :
The only other potential boondocking spot besides the boat launch is on Salmon Glacier Road at this large turnout where I personally wouldn't want to boondock at (5 miles in the other direction from the bear viewing site) as the roadway was a little too uneasy for my camper rig with all the climbing, intermittent rough spots and too much construction truck traffic for my liking as this is where I turned around as I decided not to attempt Salmon Glacier in my camper rig, although I seen a few cabover campers and a class C motorhome that did commute there as they crossed paths with me heading back into Hyder :
There is a bus that provides a ride there as they quoted me $60 as I was not willing to pay that amount for a ride to see a glacier, so it gives me another reason to return to Hyder again someday to fill that bucket list (while finding another option to get there without getting extorted for $60).