Earlier this week, Speaker of the House of Commons John Bercow used a 400-year-old Parliamentary rule from 1604, which stopped Prime Minister Theresa May from holding another MP vote on her Brexit deal when she would have liked.
Mr Bercow claimed that a law in Parliament's ancient rule book - called Erskine May - says that Mrs May couldn't get MPs to vote for a third time unless her deal was significantly changed.
BBC political editor Laura Kuenssberg explains that the rule says: "Governments are not meant to be able to keep asking parliament the same question, in the hope of boring MPs [to do what they want] if they keep saying no."
Some people were angry that Mr Bercow did this.
This got us thinking about old laws that exist in the UK that you might not know about.
There are some rules about behaviour on pavements that you might not know about.
Section 54 of the Metropolitan Police Act says that you are not allowed to carry a plank along a pavement in London, unless you are unloading it from a vehicle! The rule also includes casks, tubs, hoops, wheels, ladders, poles and placards.
It also says that you can't feed or clean your horse on a pavement or a public place if it's going to annoy people.
The same law also says that you're not allowed to fly a kite if it's going to irritate other members of the public, or slide on ice and snow if there's a risk that it might hurt someone.
The rules are all designed to help the flow of pedestrians and keep everybody safe, although some seem a little outdated now!
Have you ever been in a city and an adult has needed to hail down a passing taxi?
Well, the law actually says that taxis are only actually allowed to get business and take passengers when they are at a standstill, so technically it's sort of against the law to be driving around with an 'available' light on and call over a cab that's moving.
But the police have come to accept that taxis are only inviting business once they're actually pulled over, so that makes it OK.
Did you know that it is against the law in the Metropolitan Police Act 1854 to ring a doorbell or knock at a door if you don't have a reason to?
So if you've ever heard of the game knock-and-run, well, think again before playing it!
Even the carpets and rugs in your house aren't safe from old rules.
It is technically against the law to beat a carpet, rug or mat (except door mats) before 8am. We didn't know that either.
Well, handling salmon, trout and certain other fish in "suspicious circumstances", to be exact.
Section 32 of the Salmon Act 1986 says that you can't do this, as it might suggest a person is selling fish that has been caught illegally.
It's not just fish, though. If you happen to have a pig sty in your front garden and you've not kept the gate of it properly shut, you could be breaking the Town Police Clauses Act 1847.
We all know that you have to keep the noise down in a library, but did you know that the Libraries Offences Act 1898 makes it illegal to behave in a disorderly manner in a library?
You could also get in serious bother if you refuse to leave after the library or reading room is closed, according to the rules. So best sign those books out and take them home!
After a ring rot outbreak in Poland, a law was passed banning the import of potatoes into England from Poland.
You can do it, but you have to write to an inspector at least two days before you want to bring your potatoes into the country with lots of information, including the quantity and what you intend to use them for.
If you're lucky enough to visit the UK Parliament, whatever you do, don't wear armour.
That's against the law too, according to a rule written in 1313.