idiom for saying "by virtue of their $nothing [anticlimax]"?

Question

In German, there is an idiom "kraft seiner Wassersuppe" - literally translated by the force/power of his watery soup.
Is there any idiom in English that has a similar meaning or usage?

1. The idiom can be used to deflate or expose unwarranted entitlement.

   e.g. The mayor thinks he can raise the dog tax kraft seiner Wassersuppe.
   = He thinks he has/should have the power legitimation to do this, but really he's lacking any legitimation/power to do so. He'd actually need the town council to do so. Nevertheless, the dog taxes will be raised - and the town council will not even protest that they weren't heard.

2. It can also be used to emphasize that someone does something without need of the slightest further empowering reason or legitimation.

   e.g. The mayor can raise the dog tax kraft seiner Wassersuppe
   = The mayor can do that because they are mayor. No further legitimation needed.

3. There can be a combination of both by having a skeptic connotation to 2.:

   e.g. The mayor can raise the dog tax kraft seiner Wassersuppe
   = The mayor can do that because they are mayor, but I don't see why a mayor should have the power to raise dog taxes.

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Kraft = by virtue of here creates a quite solemn, lofty start and sets an expectation of a compelling reason for power coming. But what follows is that the expectation is deflated with the anticlimax of something that doesn't carry any power.

Wassersuppe is a soup based only on water in contrast to soups based on broth, stock or milk. I.e., water, a starchy ingredient and possibly some vegetables. Certainly not even little pieces of meat. Too thin to be considered a porridge. Think of a kasha served with so much water that the grains swim freely.
So basically, the poorest of poor people's food, something as non-nourishing as one could get within what can be called food.

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update wrt. @FumbleFingersReinstateMonica's comments: The idiom typically does not question the mayor's ability to raise the dog tax. Power above may not have been the best description. I was thinking of the power e.g. a constitution gives to a government, in contrast to the factual power such a government has.

It's more in line with:

Someone: Mayor, why do you raise the dog tax?
Mayor: Because I can.

Answer 1

There are many good suggestions given above for Wassersuppe, but I believe the closest English translations are:

He did it on a whim.

or sometimes

On a lark

Even more terse, but somewhat antiquated and decidedly a little silly:

He raised the tax willy-nilly.

I can't think of an idiom that plays the same language game of "let-down" to imply that the action should have been substantiated.

But we will very often say:

They mayor, in his infinite wisdom, has decided to....

and convey with vocal stress that the mayor likely has exactly zero wisdom, or no good reason. But this would not be good use if the mayor did have the required authority.

Answer 2

I haven't found an exact equivalent, but here are some suggestions.

1. Entitlement:

• "He thinks he can do that simply on his own say-so."
• "He claims some sort of authority to do that."
• "He is doing that simply on his own so-called 'authority'."

2. Without further authority:

• "The mayor can raise the dog tax off his own bat."
• "The mayor can raise the dog tax simply on his own say-so."

3. Sceptical:

• "The mayor claims some sort of authority to raise the dog tax."
• "The mayor can raise the dog tax simply on his own so-called 'authority'."
• "It seems the mayor can raise the dog tax by mere diktat."

Answer 3

One thing that comes to mind is a reiteration of the person’s identity, highlighting that this alone is enough for them to be empowered to do something.

The mayor can raise dog taxes because he’s the mayor.

John can just do it because he’s John.

I suppose the only thing lacking here is the humorous aspect; the phrase I’ve given is a bit more serious and perhaps a bit more defeatist/resigned, though it may also be said in a sarcastic tone to convey skepticism.

Also, with regards to [1], what comes to mind is the saying that someone is “all talk”, which can mean that the person talks as though they are going to do something, but in truth, they won’t, or lack the capacity to do so.

Answer 4

The closest idiom I can think of is "you and whose army?", but it's much more limited in usage than your examples. It's closest to meaning 3 - usually used as a response to a threat, or a plan, which you think the speaker has no power or resources to carry out:

- Tomorrow I'm going to raise dog taxes.

- Oh, yeah? You and whose army?

It's also typically used in the second person - COCA shows no other results, and Google has few for "he" and "they", and only four for "she".