I would like to answer even though I am a non native speaker. ( mainly targeting to support the answer by murally maddy.
transitive verb
1
a : to draw together or cause to converge : condense, consolidate
b (1) : to diminish in size, amount, extent, or number : make smaller : lessen, shrink
(2) : to decrease the volume and concentrate the flavor of (as a gravy) by boiling off excess liquid (3) : to concentrate or decrease the volume of (as crude petroleum) by removing light hydrocarbons by distillation
c : to narrow down : confine, limit, restrict
d : to make shorter or divest of nonessentials : abridge, curtail
2
archaic
a : to lead back : cause to return
b : to restore to righteousness : save
3
a obsolete : redirect
b obsolete : to bring back
c : to bring to a specified state or condition by guidance or leadership
4
archaic
a : to cause to recur
b : to restore to a former condition
5
a (1) : to force to capitulate : bring under control : subdue, subjugate
(2) : to wipe out (an enemy position) : eliminate, demolish
b : to make captive or hand over
c (1) : to put under obligation : make, compel
(2) : to force to resort
(3) : to cause to succumb
d obsolete : to make more temperate : overcome
e : to cause to revert to one's possession by exercising a legal claim
6
a : to assign to or describe in terms of fundamental classification
b : to bring to a systematic form or character — used with to
c : to endow with a definite shape
d : to transfer to or as if to paper — used with to
7
a : to put back (as a herniated mass) into place
b : to restore (as elevated blood pressure) to a normal condition
c : to set (as a fracture) by restoring misplaced parts to a normal position
8
a chiefly Scots law : rescind, annul
b : to lower in grade or rank : demote
9
a : to lower in condition or status : debase, downgrade
b : to be driven by poverty or deficiency
c : to make physically weak
d : to diminish in strength or density
: such as (1) : to dilute (as a paint) with a thinner (2) : to extend (as a pigment) with an inert extender or pigment (3) : to make (a photographic negative) less dense
e : to diminish in value
10
a (1) : to change the denominations of without changing the value
(2) : to change the form of (an arithmetical expression) without changing the value
(3) : to construct a geometrical figure similar to but smaller than (a given figure)
b : to transpose from one form into another : convert, translate
c (1) : to change (an expression) from a form that is given to another that is equivalent but considered to be more fundamental or important
(2) : to change (a syllogism) to a mood in the first figure
11
a : to break down (as by crushing, grinding, or burning) : cause to disintegrate : pulverize
b archaic : to cause (a military unit) to disperse : disband
c : to separate into commercially usable elements
d : to treat (garbage) so as to recover grease and other products
12
a : to bring to the metallic state by removal of nonmetallic elements
— compare smelt
b : deoxidize
c : to combine with or subject to the action of hydrogen : hydrogenate
d : to change (a compound) by decreasing the proportion of the electronegative part
: change (an element or ion) from a higher to a lower oxidation state
: add one or more electrons to (an atom or ion or molecule)
— opposed to oxidize
13
: to transform to actuality
14
a (1) : to use an unstressed vowel (as \ə) or no vowel at all instead of (a stressed vowel) (2) : to make such alteration in (a syllable)
b : to cause the loss of a member from (a series of consonants or vowels)
intransitive verb
1
a : to become diminished or lessened; especially : to lose weight by dieting
b : to become concentrated
c : to undergo meiosis
d : to become consolidated
2
: to become converted or equated
3
: to become weakened or diluted
4
: to undergo processing especially for commercial purposes
Here, the most closest definitions to the verb "lower" are 3c, 9a, d, e, but the government is talking about the "standard" or the "requirement" of the age rule for drinking, so that either none of the definitions in the list "downgrade" or "diminish" won't fit with the OP's case. However, 3c could become a problem. Though the definition " to bring to a specified state or condition by guidance or leadership" seems to fit nicely, it is not a bit hard to call the "state" about the nuance of the OP's question, but rather be a "standard" if you closely look at the OP's question, so I would like to discard this too. If you look up the whole definition I presented, you would see the verb "reduce" has a nuance to "break/lessen physically/materially something".