Under the rule of King Jérôme, Pfeiffer worked as the Assistant Procurator General for the Court of Appeals in Cassel, and for his service, was awarded the Order of the Crown of Westphalia.

"[note 1][11] Despite his high position at court, Pfeiffer’s liberal views were well-known and over the next decades, he published an assortment of essays and treatises outlining all that was wrong with the German political system and how it needed to change.

[12] In 1830, Pfeiffer's lifelong dedication to Hesse and its people was rewarded when the Elector, William II, invested him as a Commander, 2nd Class in the House Order of the Golden Lion.

[13] Pfeiffer’s aforementioned gratitude to both the Elector and his family forced him to accept the honor, but he deeply wished to decline, fearing that this recognition by the State would, in his own words, cause him “to lose the confidence of the estates, which he had earned so far, and thus to be disturbed in his desired participation in the great constitutional work.”[note 2][13] At his request, the announcement of his investment was left out of the official government circular, allowing him to continue his political career for the time being.

Concerned with Pfeiffer’s perceived closeness to the electoral family and court, despite his liberal credentials, the other members of the Landtag declared the election invalid, which led to a conflict with Ludwig Hassenpflug that would last the rest of his life.

In 1834, Hassenpflug's manipulation led to Pfeiffer being passed over for the role Landtag President, despite having held the position provisionally for over a year, in favor of a younger and less qualified colleague.

[16] In the wake of this derailment of his political career, and feeling his own age, he submitted a formal request to retire in 1842, but was refused by the Landtag with two simple words: nicht genehmigt (not authorized).

His professional life was that of an assessor, or magistrate's assistant, but he was also something of a firebrand, publishing articles in the liberal political newspaper Der Verfassungsfreund alongside Karl Bernhardi and Ludwig Schwarzenberg.

By all accounts an accomplished poet, singer, and songwriter, Pfeiffer was particularly known during his life for composing Polenlieder, that is, songs in support and celebration of Polish freedom, which was a hot-button issue at the time.

Originally, Pfeiffer had planned to compose the opera himself, but upon realizing the breadth and labor involved, asked his friend Spohr to take over he remaining musical composition aspect of the project, to great acclaim.

The dirge for his funeral service was composed by Spohr, who also arranged a version of Selig sind die Toten to be sung by Kassel's St. Cecilia Society at the dedication of Pfeiffer's memorial.

[24] The inscription thereon was composed by his friend Karl Bernhardi, and reads as follows: Es sank der Tod in Wellen auf ihn nieder, Als seines Geistes Kraft in Blüthe stand.

[note 3] Soon after Pfeiffer's death, at the insistence of his friends who survived him, his father and sisters published a volume of his poetry entitled simply Gedichte, or Poems.