Is there a word for, "To make more strict?"

Question

We have words like strengthen which is to make stronger but that doesn't really match the meaning of what I'm looking for:

The so-and-so group _____ed its employee rules.

I'd like a word that would show that so-and-so group's employee rules became more strict or stringent. Strengthened, out of context, can mean multiple things, like the rules became more defined or the rules were updated to cover more etc.

Imagine going from a lackadaisical setting (like a school Janitor) to something of the U.S. Army. Mistakes are less tolerated and expectations are higher, etc., so a person going from such janitorial job to the army would experience a _____ing of rules.

Is there a word that fits this?

Answer 1

Tightening the rules would work exactly.

This is one of the direct definitions of the word. From OELD [1]:

[transitive] tighten something to make something become stricter

• to tighten security

• The government is to tighten controls on the sale of alcohol.

Because this is an exact definition for the word tighten, we use it to directly talk about making rules, policies, or regulations stricter.

[1] http://www.oxfordlearnersdictionaries.com/us/definition/english/tighten

Answer 2

I would use rigidified.

It's mostly different from tightened in its connotations and its grace. When you use the word tightened you have to specify what you're tightening because "tighten" usually is used as a physical verb, while rigidified is used as a metaphorical verb, and literally means "to make inflexible."