Church attire in Italy - clarification

If in doubt take a scarf.

Any length of attached sleeves cover the shoulders. Sleeveless, tank top, or something with little string straps is what would be a problem.

Last time in an Italian church was 9 months ago, but no experience with enforcement of rules - it was November, so was chilly enough to be wearing a jacket, and as for inappropriate clothing, my sense is that you know it when you see it.

Enforced or not, do what is required.

This is a sign at the St Peter's in Rome dictating what is and is not appropriate.

https://boards.cruisecritic.com/topic/2691845-help-please-vatican-dress-code-especially-men/

Another at some random church. A google will bring up others.
https://www.facebook.com/groups/visitrome/posts/1159999896334755/

You probably might get away with a cap sleeve but not sleeveless depending on the church. Some are more strict than others, and it might depend on the temperature and the whim of the attendants on duty. They were very strict at the cathedral in Milan when we were there some years ago; we saw any number of people flouting the dress rules turned away, and I've no reason to believe that has changed. Rule of thumb is if you don't want to be refused at the door after a potentially long wait, dress as instructed. Yes, you can bring a scarf to wrap around shoulders/upper arms. Same to make a sort of sarong to cover exposed knees.

LOL, it is a bit odd given the amount of flesh on display in some church-ceiling frescoes but best to do as requested in someone else's "home", eh? :O)

A few years ago, I went into a church in Italy with what I thought was an acceptable blouse. Nope! The attendant at the door made a face and forcefully sold me a crinkly oblong to wrap around my upper body. Since then I always remember to wear at least short sleeves.

Put a light scarf in your purse and wrap it around as you need.

As trelawney said, be respectful. Its not about what you might get away with.

If 'cap ' sleeve means this

https://www.nordstrom.com/s/cap-sleeve-stretch-cotton-modal-rib-t-shirt/8773318?color=ivory+egret&size=x-large&utm_term=ntcmp&utm_content=at~pla&utm_creative_format=AG~WOMENAPPAREL_PT~MSN_VS~non-video_RA~CPC_AC~NTCMP_TI~All_FF~PLA_ID~E000JIS2&msclkid=be465543b0dd1f450d483fd7277f5b8c&utm_source=bing&utm_medium=cpc&utm_campaign=CC~SITE_MA~NEM_FL~LOF_OW~JWN_TC~PDSHP_MK~USA_PK~GRD_LT~NTG_BR~NORD_PB~BGA_KT~NONBR_FF~PLA-WOMENAPPAREL_ID~B000A0HF&gclid=be465543b0dd1f450d483fd7277f5b8c&gclsrc=3p.ds&gad_source=7&gad_campaignid=23970619579

you should be OK. If it is something less, some other covering likely will be needed.

Any advice on recent rules/enforcement?

The rules have not changed. Enforcement will depend on which church you are trying to enter.

On our recent trip to Italy, every single church enforce the rules of "shoulders and knees must be covered for both men and women."
No exceptions were made. I would think that depending on how much was covered by a "cap" sleeve, that would be open to the entrance attendant's interpretation.

The suggestion to bring a light scarf/shawl for shoulders and sarong for legs is always the winning solution.
Anyway in the last weeks I noted that several controllers are less rigid, because is really very warm in Italy.

I carried a lightweight scarf for my shoulders so I could wear my preferred dress for the rest of the day. Bonus was that it worked as sun cover for some particularly bright stretches of the day as well.