Word or idiom for 'when someone does something according to the regulation'

Within the framework: while considering the rules.

Ex: We played within the framework of this game!

He won the match / played according to Hoyle. ...

According to Hoyle: In accord with the highest authority; in accord with a strict set of rules.

[The Phrase Finder]

• This isn't a country where things are cut and dried, and done according to Hoyle. [1902, Gilbert Parker in 'Donovan Pasha and Some People of Egypt']
• The opening round of the Presidents' Athletic Conference men's basketball tournament went according to Hoyle. [2007, Phil Axelrod, "District Spotlight: PAC men's basketball follows form," Pittsburgh Post-Gazette]

[both quotes given in the Wiktionary entry]

• I thought everyone played according to Hoyle. [Kid Curry]

[Alias Smith and Jones -- The Story of Two Pretty Good Bad Men – by Sandra K. Sagala, JoAnne M. Bagwell 2015]

Such a person might be called a stickler for the rules. The linked entry has it as:

a person who thinks that a particular type of behaviour is very important, and always follows it...

If someone adheres to the regulations strictly in order to purposefully harm the regulator, then the phrase is malicious compliance:

Malicious compliance (also known as malicious obedience) is the behaviour of intentionally inflicting harm by strictly following the orders of a superior while knowing that compliance with the orders will not have the intended result. The term usually implies the following of an order in such a way that ignores the order's intent but follows it to the letter. It is a form of passive-aggressive behavior.

How about on the up-and-up?

From M-W:

up-and-up: an honest or respectable course -- used in the phrase on the up-and-up

From The Free Dictionary:

on the up-and-up: legitimate; open and aboveboard. Is this deal on the up-and-up? What's the catch? Everything I do is on the up-and-up. I am totally honest.

Your example:

He won the match on the up-and-up.

Jobsworth (noun) informal disapproving UK:

someone who always obeys all the rules of their job even when they cause problems for other people or when the rules are silly

Jeremy Taylor - Jobsworth

That person is acting according to the letter of the law

The precise wording rather than the spirit or intent. For example, Since it was the first time he'd broken the rules, the school decided to ignore the letter of the law and just give him a warning. [Late 1500s]

— Dictionary.com

Compliant

As in within compliance standards.

https://www.dictionary.com/browse/compliant?s=t

"He won honestly." The opposite is "cheater" as discussed in GolfDigest website

"Most golfers say they are honest; in 10 of our 15 situations, the majority say they never bend the rule in question."

NYTimes tells of Bobby Jones' calling a penalty on himself. When asked why, he said: "Well, you might as well have praised a man for not robbing a bank."

I don't see this level of honesty in any other sport. Honesty in most other sports is dictated by referees (although it took a while to catch Lance Armstrong).

The word "gracious" could never be applied to the play of that line-call disputer John McEnroe. New technology must be credited for today's improved behavior, not nicer players.

Here are some befitting idioms.

• By the book

exactly according to rules or the law

• Above board

openly and legitimately

• Fair and square

honestly and according to the rules

With that, here are some relevant words.

• Compliance

the act or process of complying to a desire, demand, proposal, or regimen or to coercion

• Stickler (for sth)

a person who thinks that a particular quality or type of behaviour is very important and expects other people to think and behave in the same way