Even if you love exclamation marks as much as Elaine from Seinfeld, when drafting a pleading, there's really only one time when using one is appropriate. And no, it's not when you really need to put opposing counsel on blast.
Much like vulgarity, or emojis, the use of exclamation marks should only be done when using quotes. Just like Elaine, you'll likely face some wrath, or ridicule, if you don't heed this warning, and especially if you overuse them.
Really? Yes, Really!
Legal writing may not have to be boring, cold, and dry, but short of quotes, there's no reason to be using exclamation points. As the Daily Journal explained, using an exclamation point "is the equivalent of barking at judges, shouting, or gesticulating wildly."
When it comes to making an impassioned plea to the court, using an exclamation point is the epitome of telling rather than showing. While one or two in a pleading might not even merit a mention, it's very likely that a judge and their clerks will notice it sticking out like a sore thumb, and judge your writing style, or even the merits of your argument, for it.
Sure, using bold or italics to provide some emphasis here or there can be helpful, but using an exclamation point is almost like using all-caps for emphasis, it's distracting and can be confusing to a reader. And your pleading should not distract or confuse, especially with the writing style.
How to Quote an Exclamation
If you're quoting a relevant exclamation that a person made, then yes, you should probably include the exclamation mark. And when you do so, the punctuation goes inside the quotation mark. "Like this!"
Additionally, depending on the quote, you may wish to highlight the fact that it is an exclamation by italicizing the exclamation portion of the quote to cue the reader in to the change in narrative tone.