Empire patrol are guards, soldiers and mercenaries that are loyally bound to serve under the King in STWALT. They are located at the castle and towers, often placed as garrisons or to thwart any invasions (if there are at least).
Their primary functions are to protect the land from evils or working as a guard, at the castle and prisons. Most of the time, they collect taxes (25 golds) from peasants and travellers alike, making them the most hated group in the kingdom, for the reason of keeping their passage and roads safe from monsters.
An Empire Patrol have a random attack power and HP, which indicates their training as an conscript, recruit, veteran or an elite soldier.
Fighting an Empire Patrol will certainly make you a criminal, but if you are a rebel and don't have enough gold, you could just kill them. It gives you 1xp. When you are in prison, you can bribe them, but there is a chance they will not accept it and your sentence can be prolonged. And never, ever try to profess your innocence in front of the guards (a.k.a. Empire Patrol) because you only have basic 5% chance per level to succeed. Unless you feel lucky, try it then.