Thou Shalt Not Pass is a Side Quest on the border between Velen and Novigrad in The Witcher 3.

Your journey will eventually force you to go to Novigrad. Due to the ongoing war, travel between the Free City of Novigrad and Velen has been restricted to all except to those who have proper paperwork. Speak to the guard at the gate to receive the quest. There are several ways of obtaining the paperwork (this list might not be complete, add as additional ways are discovered).

• Talk to the Shady Merchant just South of the crossing among the Refugee Camp and undertake the Fake Papers quest to try and score a deal on the papers (100 gold for the pass, or 50 using the Delusion Axii Sign skill.)

• Talk to the Shady Merchant and agree to help his brother nearby in the Bitter Harvest quest to reduce the price of a pass to just 25 gold.

• Certain quests, such as Family Matters, will give you the paperwork during the quest or as a reward.

Once you have the paperwork, speak to the guard at the gate to let you through. You are now able to freely travel between Novigrad and Velen.