How can law enforcement access a bank account without notifying the account holder?

In almost every country that provides banking, there is a systematic method of allowing LEA (Law Enforcement Agencies) access to your bank account.

Despite what you may hear or assume, regardless of a developed country or a developing country, a bank account is a very well protected asset.

In order for LEA to get access to it, they usually have to get a court order / legal injunction / subpoena / insert-your-legal-terminology here from a competent authority before access to the bank account is allowed.

In most cases, the bank is legally barred from disclosing such an on-going investigation to you.